Description: technologyComment of gold mine operation and refining (SE): OPEN PIT MINING: The ore is mined in four steps: drilling, blasting, loading and hauling. In the case of a surface mine, a pattern of holes is drilled in the pit and filled with explosives. The explosives are detonated in order to break up the ground so large shovels or front-end loaders can load it into haul trucks. ORE AND WASTE HAULAGE: The haul trucks transport the ore to various areas for processing. The grade and type of ore determine the processing method used. Higher-grade ores are taken to a mill. Lower grade ores are taken to leach pads. Some ores may be stockpiled for later processing. HEAP LEACHING: The ore is crushed or placed directly on lined leach pads where a dilute cyanide solution is applied to the surface of the heap. The solution percolates down through the ore, where it leaches the gold and flows to a central collection location. The solution is recovered in this closed system. The pregnant leach solution is fed to electrowinning cells and undergoes the same steps as described below from Electro-winning. ORE PROCESSING: Milling: The ore is fed into a series of grinding mills where steel balls grind the ore to a fine slurry or powder. Oxidization and leaching: Some types of ore require further processing before gold is recovered. In this case, the slurry is pressure-oxidized in an autoclave before going to the leaching tanks or a dry powder is fed through a roaster in which it is oxidized using heat before being sent to the leaching tanks as a slurry. The slurry is thickened and runs through a series of leaching tanks. The gold in the slurry adheres to carbon in the tanks. Stripping: The carbon is then moved into a stripping vessel where the gold is removed from the carbon by pumping a hot caustic solution through the carbon. The carbon is later recycled. Electro-winning: The gold-bearing solution is pumped through electro-winning cells or through a zinc precipitation circuit where the gold is recovered from the solution. Smelting: The gold is then melted in a furnace at about 1’064°C and poured into moulds, creating doré bars. Doré bars are unrefined gold bullion bars containing between 60% and 95% gold. References: Newmont (2004) How gold is mined. Newmont. Retrieved from http://www.newmont.com/en/gold/howmined/index.asp technologyComment of primary zinc production from concentrate (CA-QC): Hydrometallurgical process Sulphide concentrates are roasted first in fluidized bed roasters to produce zinc oxide (calcine) and sulphur dioxide. Roasting is an exothermic process and no additional fuel is used to sustain the reaction, the heat generated is recovered to produce steam. Calcine is then sent to the leaching step. Roaster gases are treated in hot electrostatics precipitators to remove dust. The remaining dust and volatile metals such as mercury and selenium are removed in the wet section of the acid plant through a cooling tour, a mist precipitator and a mercury tower (Boliden mercury removal processs). The sulphur dioxide is then converted to sulphuric acid in a conventional recovery system (converted and absorbing tower). Leaching of the calcine is carried out in a number of successive stages using a gradually increasing strength of hot sulphuric acid. The initial stages dissolve the major part of the zinc oxide and the other stages dissolve the zinc ferrite (ZnO.Fe2O3) and convert iron into Jarosite (sodium Jarosite). Zinc sulfate (ZnSO4) entering the electrolysis stage produce electrolyte (H2SO4) that is returned to leaching plant. Other metals are also dissolved during the process and are removed after leaching. Iron is the major impurity, which is precipitated in the form of Jarosite. Overall waste: The production of metals is related to the generation of several by-products, residues and wastes. Relatively large quantities of iron based solids, depending on the iron content, are generated by the leaching process (6.14E-1 kg Jarosite/kg zinc). Cement is added to the Jarosite to produce Jarofix (an inert waste). Solid residues also arise as the result of the liquid effluents treatment. The main waste stream is gypsum (CaSO4) and metal hydroxides that are produced at the wastewater neutralization plant. Mercury and selenium residues arise from the weak acid bleed treatment from the acid plant. Selenium can be recovered from these residues depending on the market demand for this metal. Overall emissions: The emissions to air can either be stack emissions or fugitive emissions. Stack emissions are normally monitored continuously (SO2) or periodically (other emissions) and reported. The main emissions to air from zinc production are sulphur dioxide (SO2) and particulate matters including metals. Main emissions to water are metals and their compounds. The monitored metals are zinc, cadmium, lead, mercury, selenium, copper and arsenic. technologyComment of primary zinc production from concentrate (RoW): The technological representativeness of this dataset is considered to be high as smelting methods for zinc are consistent in all regions. Refined zinc produced pyro-metallurgically represents less than 5% of global zinc production and less than 2% of this dataset. Electrometallurgical Smelting The main unit processes for electrometallurgical zinc smelting are roasting, leaching, purification, electrolysis, and melting. In both electrometallurgical and pyro-metallurgical zinc production routes, the first step is to remove the sulfur from the concentrate. Roasting or sintering achieves this. The concentrate is heated in a furnace with operating temperature above 900 °C (exothermic, autogenous process) to convert the zinc sulfide to calcine (zinc oxide). Simultaneously, sulfur reacts with oxygen to produce sulfur dioxide, which is subsequently converted to sulfuric acid in acid plants, usually located with zinc-smelting facilities. During the leaching process, the calcine is dissolved in dilute sulfuric acid solution (re-circulated back from the electrolysis cells) to produce aqueous zinc sulfate solution. The iron impurities dissolve as well and are precipitated out as jarosite or goethite in the presence of calcine and possibly ammonia. Jarosite and goethite are usually disposed of in tailing ponds. Adding zinc dust to the zinc sulfate solution facilitates purification. The purification of leachate leads to precipitation of cadmium, copper, and cobalt as metals. In electrolysis, the purified solution is electrolyzed between lead alloy anodes and aluminum cathodes. The high-purity zinc deposited on aluminum cathodes is stripped off, dried, melted, and cast into SHG zinc ingots (99.99 % zinc). Pyro-metallurgical Smelting The pyro-metallurgical smelting process is based on the reduction of zinc and lead oxides into metal with carbon in an imperial smelting furnace. The sinter, along with pre-heated coke, is charged from the top of the furnace and injected from below with pre-heated air. This ensures that temperature in the center of the furnace remains in the range of 1000-1500 °C. The coke is converted to carbon monoxide, and zinc and lead oxides are reduced to metallic zinc and lead. The liquid lead bullion is collected at the bottom of the furnace along with other metal impurities (copper, silver, and gold). Zinc in vapor form is collected from the top of the furnace along with other gases. Zinc vapor is then condensed into liquid zinc. The lead and cadmium impurities in zinc bullion are removed through a distillation process. The imperial smelting process is an energy-intensive process and produces zinc of lower purity than the electrometallurgical process.
Types:
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Comment: This is a market activity. Each market represents the consumption mix of a product in a given geography, connecting suppliers with consumers of the same product in the same geographical area. Markets group the producers and also the imports of the product (if relevant) within the same geographical area. They also account for transport to the consumer and for the losses during that process, when relevant. This is the market for 'zinc', in the Global geography. In this market, expert judgement was used to develop product specific transport distance estimations. This market is supplied by the following activities with the given share: gold mine operation and refining, SE: 0.00196582324623316 primary zinc production from concentrate, CA-QC: 0.0205352195300018 primary zinc production from concentrate, RoW: 0.977498957223765 generalComment of gold mine operation and refining (SE): This dataset was created by merging two separate multi-output datasets from ecoinvent database v2; "mining, gold-silver-zinc-lead-copper deposit" and "refining, copper-zinc-lead-gold-silver, in smelter". This dataset describes the joint production of gold, silver, copper, lead and zinc. Both mining and refining are included in this activity. The data on mining corresponds to Swedish mines Aitik, Boliden and Garpenberg, which produce gold, silver and other metals. Data quality for emissions into air / water, as well as disposal of tailings, is low. Regarding the refining; gold and silver are supposed to be treated in the PGM plant in Rönnskär, whereas the other metals are supposed to undergo other treatments. A high share of the production is recycled metal, e.g. 74% for gold. generalComment of primary zinc production from concentrate (RoW): The multi-output "primary zinc production from concentrate" process includes all steps required to produce special high grade zinc from zinc concentrate using the electrometallurgical and pyrometallurgical (less common) processes. Electrometallurgical zinc smelting includes roasting, leaching, purification, electrolysis, melting, and sulfur dioxide gas treatment. Pyrometallurgical zinc smelting includes sintering, leaching, refining, and sulfur dioxide gas treatment. The dataset describes the production of zinc and additional co-products, primarily sulfuric acid. Data is based on a study undertaken by the International Zinc Association (IZA) in conjunction with thinkstep (the LCA practitioner) for reference year 2012. Participating companies provided annual primary data on inputs and outputs for each process step, which was aggregated into a single production-weighted dataset. The below images present the system boundary in relation to the primary product, special high grade zinc. imageUrlTagReplacec1fef210-e0fd-48fd-9cea-351f6a190ca8 imageUrlTagReplace27d4da96-9dfb-45d5-ac34-9f40810abac8 generalComment of primary zinc production from concentrate (CA-QC): This dataset represents the production of high grade (SHG-Special High Grade) primary zinc by hydrometallurgical processes. Specific data were collected from the only producer in the Québec region, for the years 2011-2012. Primary zinc is produced in the form of ingots and shot, respectively used as coating in steel work/die cast and for electroplating. About 25% of the produced zinc is in the form of an aluminium alloy. The zinc concentrate, coming from all around the world (e.g. Canada (Québec and Ontario), Australia), is transported to the site by train or by ship and truck and mixed on site. The site is able to treate zinc concentrate contaminated with mercury and selenium but cannot recover silver and lead. Contrary to the GLO dataset, this dataset does not include waste contaning indium ("indium rich leaching residues, from zinc production" by-product flow).
Origin: /Bund/UBA/ProBas
Tags: Hirsch ? Zement ? Aluminiumoxid ? Festmist ? Sinterung ? Zinksulfat ? Zinksulfid ? Eisen ? Gold ? Kobalt ? Ferrit ? Aluminium ? Hydroxid ? Silber ? Sulfid ? Zinkoxid ? Ammoniak ? Bleioxid ? Kupfer ? Brennstoff ? Abfallbehandlung ? Main ? Metallhydroxid ? Metalloxid ? Quecksilber ? Raffination ? Pflanzensamen ? Sauerstoff ? Schwefelsäure ? Selen ? Elektrolyt ? Wasserdampf ? Zink ? Cadmium ? Arsen ? Staub ? Blei ? Elektrofilter ? Schwefel ? Kohlenstoff ? Koks ? Brüden ? Lastkraftfahrzeug ? Partikelemission ? Cyanid ? Sickerwasser ? Metall ? Elektrolyse ? Abfalltransport ? Schimmel ? Tagebau ? Kohlenmonoxid ? Schwefeldioxid ? Wirbelschicht ? Gasförmiger Stoff ? Tankbehälter ? Nebel ? Diffuse Emission ? Goldbergbau ? Schmelzofen ? Erzverhüttung ? Gips ? Lauge ? Explosivstoff ? Mühle ? Destillation ? Stahl ? Nebenprodukt ? Reinigungsverfahren ? Höhle ? Abfall ? Abwasser ? Abfallart ? Erz ? Kühlturm ? Legierung ? Niederschlag ? Ofen ? Manufacture of basic precious and other non-ferrous metals ? Manufacture of basic metals ? Manufacturing ?
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